This invention relates to fluid flow indicators of the general type disclosed, for example, in U.S. Pat. Nos. 2,847,969 and 5,012,840 and in British Patent No. 678,762. In such an indicator, it is sometimes desirable to provide for a visual indication of a very low fluid or liquid flow rate, for example, 0.2 gallons per minute (GPM). It is also sometimes desirable to provide for an electrical or electronic indication of the fluid flow in order to operate an electrical alarm or a power operated apparatus such as, for example, a machine which requires a flow of cooling liquid or water as in a welding machine or a die cast machine or an injection molding machine. In such a machine, if the cooling water stops flowing for some reason, it is highly desirable to actuate an electrical alarm or immediately stop the machine. While some compact fluid flow indicators provide a visual indication of fluid flow, they are not sensitive to very low flow rates and/or do not provide an electrical signal if fluid flow stops.
The present invention is directed to and improved and compact fluid flow monitor and indicator which provides for both a visual indication and an electronic indication of fluid flow and which is also simple in construction and may be easily installed on a control panel. The indicator of the invention is also sensitive to low flow rates, such as 0.2 GPM, and may be adapted for substantially higher flow rates such as 18 GPM. The flow indicator of the invention further provides for a long maintenance-free service life and results in no significant fluid pressure drop across the indicator.
A fluid flow monitor and indicator constructed in accordance with a preferred embodiment of the invention, includes a metal or brass body having a threaded inlet port and a threaded outlet port which extend to corresponding inlet and outlet chambers within the body. A semi-spherical plastic liner is recessed within the body and has small parallel ports extending from the inlet chamber and from the outlet chamber. A dome-shaped transparent lens is sealed to the body and cooperates with the liner to define a generally spherical fluid circulating chamber in which is located a small fluid sensing element in the form of a ball having crossing holes therein. The metal body is secured to and supported by a mounting base or plate which also supports a power operated optical sensor having fiber optic cables extending to opposite sides of the lens in order to sense movement of the ball within the fluid circulating chamber. The optical sensor provides an electrical signal for operating an alarm or for automatically controlling a machine which requires a fluid flow.
Other features and advantages of the invention will be apparent from the following description, the accompanying drawings and the appended claims.